Naila Amin, 26, holds a book from one of the classes she is taking at Nassau Community College in Garden City, Feb. 2. Ms. Amin, who was forced into marriage at the age of 15 to a 28-year-old cousin in Pakistan who beat and mistreated her, aspires to become a social worker and open a group home for girls trying to avoid or recover from forced marriages.

In the state of Virginia, a 13-year-old child can legally marry an adult twice her age, and all that's needed is a clerk's consent, provided she is pregnant and has parental consent.

That is expected to change this week, however, after Virginia Gov. Terry McAuliffe signs reform legislation. If he signs the bill passed Tuesday, the Virginia law may be the first domino in a chain of legislatures around the nation.

Similar bills are in the works in New York (A. 8563), Maryland (H.B. 911), and New Jersey (A. 3091) where, as in many other states, marriage age limits set at 16 to 18 years old are easily set aside through exceptions based on parental and/or judicial consent, or pregnancy.

“A child who’s 13 and pregnant – it’s rarely the case that the 13-year-old is marrying a 17-year-old,” said State Sen. Jill Vogel (R), who sponsored Senate Bill 415 in Virginia, to local media. ”It’s more often the case that it is a child marrying somebody decades older than they are.”

Proponents of this legislation want to see it in all 50 states, because they say that victims of forced and child marriage can face severe and lifelong consequences – including physical, psychological, sexual, and economic abuse, mental health problems, and a loss of freedom to choose and make their own futures.

“The common assumption we are seeing is the belief that child marriages don't happen that often – and when they do, it's believed they are Romeo-and-Juliet-aged peers, which is not what we are seeing happen here," says Jeanne Smoot, senior policy counsel for Tahirih.

"The data shows it’s girls under the age 18, including some who are well under age 15, being married to adults and one-third of the time that adult is over 21."

The Tahirih study found that nearly 4,500 children were married in Virginia between 2004 and 2013, and more than 200 of them married at age 15 or younger. About 90 percent of the underage spouses in Virginia are girls. Among the very youngest (15 or younger), there are 13 times more underage brides than grooms.

In Maryland, Tahirih found that, since 2000, more than 3,000 children were married. About 85 percent of the underage spouses were girls. Particularly alarming was a 2012 case in which a 16-year-old-girl married a man in his late 30s.

“In 2006 the State of Georgia did away with the pregnancy exception to their underage marriage law, to respond to cases in which those being investigated on charges of statutory rape had tried to avoid punishment by simply marrying the child they were accused raping,” says Ms. Smoot.

In New York state, 16- and 17-year-olds may marry with “parental consent” and 14- and 15-year-olds may wed with judicial approval. The data show that 3,853 children were married between 2000 and 2010.

State data from 2011, excluding New York City, showed that a 14-year-old married a 26-year-old, a 15-year-old was wed to a 28-year-old, another 15-year-old was wed to a 25-year-old, and a third 15-year-old married someone age “35 to 39.”

All of those marriages were approved by New York judges.

Sonia Ossorio, President of NOW New York, says that when she met with New York Gov. Andrew Cuomo about the issue, “He was strongly supportive of the bill. He said it’s time for something to be done to end this.”

Overall, there has been little public opposition to anti-child-marriage legislation. “There has been no organized push-back against our efforts," says Fraidy Reiss, founder of Unchained at Last. "I don’t think anybody wants forced marriage to continue.”

Between 1995 and 2012, 3,499 New Jersey children were married, says Ms. Reiss. Most were age 16 or 17 and married with parental consent, but 178 were between ages 10 and 15, meaning a judge approved their marriages. Of those children, 91 percent married adults, often with age differences that could have triggered statutory-rape charges.

“The worst case in New Jersey was that of a judge in 2006 approving the marriage of a 10-year-old boy to an 18-year-old woman,” Reiss says. “A judge in 1996 allowed a 12-year-old girl to marry a 25-year-old man.”

In Texas from 2009 to 2013, some 718 children between the ages of 15 and 17 were married. Texas, with its every-other-year legislative cycle, will see this legislation next year.

“That is just the few states where we have completed the data examination,” says Reiss. “We intend to examine every state in the nation. We are also looking for more partners to help us protect children.”

Globally, 88 percent of countries set 18 as the minimum marriage age, but more than half allow minor girls to marry with parental consent, according to the World Policy Center.

[Editor's note: This story was edited to clarify legal issues in both Virginia and Georgia.]